Leaks or breaks in a vessel, such as a pipeline, that can be transporting a fluid or gaseous material over long distances, must be detected in order to avoid loss of the material, and, in many cases, for safety and environmental considerations. Moreover, many such pipeline vessels are located in outlying areas with no on-site attendant, and therefore a reliable device and method for remote detection is necessary and desirable.
If, on the other hand, such devices and methods indicate erroneously that a leak or break has occurred, a false alarm is sounded. False alarms can be expensive to the pipeline operator, as they could cause false shut-downs of the pipeline and/or unnecessary repair trips by maintenance personnel. Therefore, while it is desirable to provide a device and method that is sensitive to detection of those vessel characteristics whose magnitude change upon the occurrence of a leak or break (such as pressure, flow and temperature), care must be taken to preclude false detection possibilities.
Currently available leak detection devices, such as the pressure based sensing device disclosed in U.S. Pat. No. 4,012,944, can be sensitive enough to detect most unacceptable operational conditions, but they do not have an accurate method of determining if the unacceptable condition results from something other than a leak or break, and therefore the potential for false alarms exists. Devices as this measure pressure and calculate both rate of pressure change and total pressure change, and from these measurements determine if a leak or break has occurred.
Moreover, most commercially available devices for detection of pipeline leaks or breaks are at least in part mechanical in nature, often giving rise to such problems as a lack of sufficient sensitivity, and greater susceptibility to corrosion, condensation and blockage.
Comparison of rates of change at successive preselected timed intervals has been found to greatly facilitate recognition of instances of false triggering and the avoidance of false alarms without the sacrifice of sufficient sensitivity to detect substantially all leaks and breaks, particularly when utilized in conjunction with known leak and break detection techniques. Also, this method of operation may be implemented wholly electronically, avoiding the difficulties that may plague devices with mechanical components, and using any desired characteristic, of course including the most common characteristic of pressure.